Electronic devices are commonplace in today's society. Example electronic devices include cell phones, tablet computers, personal digital assistants, smart watches, kiosk display screens, and the like. User interfaces of such electronic devices may often have touch-based input surfaces that use resistance-based sensors, such as of strain or another physical parameter, to detect inputs. Resistance-based sensors may detect a resistance value or changes in the resistance value.
For example, resistance-based strain sensors often comprise a thin film having conductive path. When the film is attached to a deformable surface, deflection of the surface alters or stretches the conductive path, changing its resistance. The change in resistance correlates with the force on the deformable surface, and can be detected by circuitry such as a Wheatstone bridge. However, this approach creates scaling problems as the number of such strain sensors is increased since conventionally a bridge circuit uses a dedicated applied voltage source for each resistance to be measured. When multiple strain sensors are to be measured, either a single voltage source and bridge can be applied sequentially to the sensors, or multiple voltage sources and bridges can be used. The former case can lead to time delays in measuring touch inputs on an input surface. The latter case can lead to unacceptable circuit size and complexity.